Question: What chemical compound with the lowest median lethal dose has safety classification and labelling of NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response?
Paraphrase: What chemical compound with the lowest median lethal dose has protection classification and labelling of NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response?
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q11173 . ?ent wdt:P2240 ?obj . ?ent wdt:P4952 wd:Q51139288. } ORDER BY ASC(?obj)LIMIT 5 
Answer: acetone cyanohydrin, arsenic trihydride, arsenic trihydride, acrylic acid, arsenic trihydride